Productivity-climate coupling recorded in Pleistocene sediments off Prydz Bay (East Antarctica)

Abstract

Export-production in the Southern Ocean is thought to be tightly correlated with atmospheric CO2 fluctuations over geological times. Relevant studies are, however, mainly confined to the Atlantic and Pacific sectors of the Southern Ocean and often only cover the last glacial-interglacial cycle. Here, we present a sediment record retrieved off Prydz Bay (East Antarctica) spanning the last ~520kyrs. We show that the distribution pattern of local export production is closely coupled with global climate change on orbital time scales. We propose that the dominant factors controlling local export production include the amount of nutrients supply from the ocean interior and the extent of sea ice cover, thus representing the combined history of deep water exposure/ventilation and the sea ice coverage in the studied area. Sharp increases in the local export production coincide with abrupt increase in atmospheric CO2 concentrations during deglacial periods, indicating drastic outgassing of the upwelled deep water in the Southern Ocean. Gradually decrease in the export production following interglacial peaks concurs with decrease in deep water exposure/ventilation and increase in sea ice cover, explaining the early decline in atmospheric CO2 over a glacial-interglacial cycle.